The present invention relates to novel siloxanes. More particularly, the present invention relates to a siloxane which contains at least one benzotriazolyl/tetraalkylpiperidyl substituent, i.e., a single substituent which contains both a benzotriazolyl group and a tetraalkylpiperidyl group.
Prior to the discovery of the surface-segregatable, melt-extrudable thermoplastic compositions described in co-pending and commonly assigned application Ser. No. 07/181,359, in which the siloxanes of the present invention are useful, the only practical way to stabilize polymers against actinic radiation has been to incorporate throughout the bulk of the polymer a stabilizing additive, i.e., an additive which either absorbs ultraviolet radiation or inhibits degradation. See, by way of illustration only, U.S. Pat. Nos. 4,087,399 to M. Hamada et al., 4,156,674 to S. Sumimura, and 4,554,310 to J. H. Wengrovius and L. W. Niedrach, which relate to the incorporation of benzotriazoles in polymers, and U.S. Pat. Nos. 4,299,926 to J. Rody and M. Rasberger, 4,294,963 to J. Rody, 4,661,594 to M. Rasberger et al., 4,629,682 to D. G. Leppard and J. Rody, 4,426,472 to G. Berner, and 4,426,471 to G. Berner, among others, which relate to the incorporation of tetraalkylpiperidines in polymers. Even though efficient stabilizers may be used, such as the benzotriazole and tetraalkylpiperidine stabilizers disclosed in the foregoing patents, a bulk incorporation procedure does not concentrate the stabilizer at or near the surface where it is most needed. Such shortcoming generally was overcome only by using very high levels of additive. This approach, however, can be prohibitively expensive and also can lead to thermal degradation, processing, and/or polymer performance problems associated with such very high levels of additive.
As noted above, novel benzotriazolyl-substituted, siloxanes are described in application Ser. No. 07/181,624 and novel tetraalkylpiperidyl-substituted siloxanes are described in application Ser. No. 07/181,623. Such compounds can be incorporated into thermoplastic polymers as described in said application Ser. No. 07/181,359. The resulting compositions exhibit improved stability upon exposure to actinic radiation. The first type of compounds absorbs ultraviolet radiation, while the second type of compounds inhibits degradation induced by actinic radiation. Thus, incorporation of both types of compounds into a single thermoplastic composition is one solution to the above-described shortcoming of past polymer stabilization practices. Another solution, and the one addressed by the present invention, is to incorporate as an additive a siloxane of the present invention which rapidly segregates to the surface in a controllable manner and is both an efficient absorber of ultraviolet radiation and an effective degradation inhibitor.
It may be noted at this point that the benzotriazolyl portions of the compounds of the present invention are known. See, for example, U.S. Pat. Nos. 3,004,896 to H. Heller et al., 3,055,896 to R. J. Boyle and J. P. Milionis, 3,072,5585 to J. P. Milionis and W. B. Hardy, 3,074,910 to D. M. Dickson, 3,189,615 to H. Heller et al., 3,230,194 to R. J. Boyle, 3,253,921 to G. W. Sawdey, 3,983,132 to A. F. Strobel, 4,041,044 to H. I. White, 4,096,242 to A. F. Strobel, 4,127,586 to J. Rody and H. Heller, 4,129,521 to A. F. Strobel, 4,226,763 to M. Dexter and R. A. E. Winter, 4,283,327 to M. Dexter and R. A. E. Winter, 4,315,848 to M. Dexter and R. A. E. Winter, 4,383,863 to M. Dexter and R. A. E. Winter, 4,414,393 to M. Dexter and R. A. E. Winter, 4,447,511 to M. Dexter and R. A. E. Winter, 4,477,614 to M. Dexter and R. A. E. Winter, 4,587,346 to R. A. E. Winter and R. E. Detlefsen, 4,642,350 to A. Davatz and T. Somlo, and 4,675,352 to R. A. E. Winter and R. E. Detlefsen.
Moreover, the tetraalkylpiperidyl portions of the compounds of the present invention also are known. In addition to the patents cited above, see, for example, U.S. Pat. Nos. 4,278,590 to M. Dexter and R. A. E. Winter, 4,299,926 to J. Rody and M. Rasberger, 4,348,524 to F. Karrer and P. Moser, 4,472,547 to R. F. Malherbe, 4,511,596 to G. Berner, 4,569,997 to F. Karrer, 4,590,268 to F. Karrer, Re. 31,342 to B. Holt and D. F. Randell, and Re. 31,343 to B. Holt and D. R. Randell. See also U.S. Pat. Nos. 4,294,963 to J. Rody, 4,314,933 to G. Berner, 4,340,533 to J. Rody, 4,344,876 to G. Berner, 4,360,675 to E. Nikles, 4,377,690 to P. Moser, 4,396,769 to A. L. Ferreira and R. E. Stahlbush, 4,412,021 to F. Karrer, 4,419,472 to G. Berner et al., 4,419,512 to F. Karrer, 4,452,884 to D. G. Leppard, 4,465,765 to D. G. Leppard and J. Rody, 4,517,283 to D. G. Leppard and J. Rody, 4,518,679 to D. G. Leppard and J. Rody, 4,518,688 to D. G. Leppard and J. Rody, 4,528,374 to E. Nikles, 4,532,279 to F. Karrer, 4,556,714 to F. Karrer, 4,584,265 to D. G. Leppard and J. Rody, and 4,609,698 to F. Karrer and J. Rody.
One reference is known which discloses compounds having at least one benzotriazolyl group and at least one polyalkylpiperidyl group in the same molecule. See U.S. Pat. No. 4,481,315 to J. Rody and M. Slongo
As noted in application Ser. No. 07/181,359, polymers are used widely throughout the world to make a variety of products which include blown and cast films, extruded sheets, injection molded articles, foams, blow molded articles, extruded pipe, monofilaments, and nonwoven webs. Some of such polymers, such as polyolefins, have surface properties, such as hydrophobicity and a susceptibiltiy to degradation by ultraviolet radiation, which for many uses are either a positive attribute or at least not a disadvantage.
There are a number of uses for polyolefins, however, where the surface characteristics of the polymer either limit their usefulness or require some effort to modify the surface characteristics of the shaped articles made therefrom. Methods of affecting the surface characteristics of shaped articles made from polyolefins and other polymers are known. Representative examples of a number of such methods are described in the paragraphs which follow.
The incorporation of a surfactant in a polymer which is to be melt-processed is described in U.S. Pat. Nos. 3,973,068 and 4,070,218 to R. E. Weber. In that case, the surfactant must be forced to the surface of the fibers from which the web is formed. This typically is done by heating the web on a series of steam-heated rolls or "hot cans". This process, called "blooming", is expensive and still has the disadvantage of ready removal of the surfactant by aqueous media. Moreover, the surfactant has a tendency to migrate back into the fiber which adversely affects shelf life, particularly at high storage temperatures. In addition, it is not possible to incorporate in the polymer levels of surfactant much above 1 percent by weight because of severe processability problems; surfactant levels at the surface appear to be limited to a maximum of about 0.33 percent by weight. Most importantly, the blooming process results in web shrinkage in the cross-machine direction and a significant loss in web tensile strength.
U.S. Pat. No. 4,578,414 to L. H. Sawyer and G. W. Knight describes wettable olefin polymer fibers. The fibers are formed from a composition comprising a polyolefin resin and one or more defined surface-active agents. Such agents may be present in an amount of from about 0.01 to about 5 percent by weight. The surface-active agents can be (1) an alkoxylated alkyl phenol in combination with a mixed mono-, di-, and/or triglyceride; (2) or a polyoxyalkylene fatty acid ester; or (3) a combination of (2) with any part of (1). The preferred polyolefin is polyethylene, and all of the examples employed an ethylene/1-octene copolymer, the latter apparently being a minor component. The surface-active agents are stated to bloom to the fabricated fiber surfaces where at least one of the surface-active agents remains partially embedded in the polymer matrix. The patent further states that the permanence of wettability can be controlled through the composition and concentration of the additive package.
Polysiloxane/polyoxazoline block copolymers are disclosed in U.S. Pat. No. 4,659,777 to J. S. Riffle and I. Yilgor. The copolymers are stated to be useful as surface-modifying additives for base polymers. Such use apparently has primary reference to personal care products where the surface properties to be imparted include glossiness, smoothness, and lubricity. However, incorporation of the copolymers into fibers is stated to impart surface stain resistance, antistatic properties, flame retardancy, and wettability by both polar and nonpolar solvents. Such incorporation preferably is in the range of from about 1 to 5 parts by weight. Suitable base polymers include some vinyl polymers, acrylate polymers, polyurethanes, cellulose derivatives, and polyethylene, polypropylene, ethylenepropylene copolymers, and copolymers of ethylene with, for example, vinyl acetate. However, the single example illustrating incorporation of the disclosed copolymers into a base polymer employed as the base polymer poly(vinyl chloride), and the resulting mixture was used to cast films from solution.
U.S. Pat. No. 4,672,005 to M. E. Dyer describes a process for improving the hygroscopic, soil release, and other surface properties of a polymer substrate. The process involves contacting the substrate with an aqueous mixture containing a water-soluble vinyl monomer and a hydrophobic vinyl monomer. Polymerization of the water-soluble vinyl monomer then is initiated by a polymerization initiator, thereby forming a vinyl polymer on the surface of the polymer substrate.
U.S. Pat. No. 4,698,388 to H. Ohmura et al. describes a method for modifying the surface of a polymer material by means of a block copolymer. The block copolymer consists of a hydrophilic polymer portion formed from a vinyl monomer and a polymer portion which is compatible with the polymer material, also formed from a vinyl monomer. The block copolymer is added to the polymer material by, for example, coating the material with a solution or suspension of the block copolymer, mixing the block copolymer with the polymer material during formation of the article, forming a film from the block copolymer which then is melt-pressed or adhered to the surface of the polymer material, and coating the surface of the polymer material with powdered block copolymer.
Polymer compositions having a low coefficient of friction are described by U.S. Pat. No. Re. 32,514 to D. J. Steklenski. The compositions comprise a blend of at least 80 percent by weight of a polymer and at least 0.35 percent by weight of a crosslinked silicone polycarbinol. The polymer preferably is a blend of cellulose nitrate and a hydrophobic acrylate polymer. The silicone polycarbinol in general is a hydroxy-terminated polysiloxane or hydroxy-substituted polysiloxane. The compositions typically are prepared by dissolving the polymer or polymer blend, silicone polycarbinol, and crosslinking agent in a suitable solvent and casting a film from which the solvent is allowed to evaporate.
Canadian Patent No. 1,049,682 describes the inclusion in a thermoplastic polymer of from 0.1 to 10 percent by weight of a carboxy-functional polysiloxane. Suitable thermoplastic polymers include polyolefins. Such inclusion is stated to enhance the properties or characteristics of the thermoplastic polymer in one or more ways. By way of illustration, products or articles made from the polymer mixture were stated to have self-lubricating properties and increased resistance to wear. For molded articles, less friction during transfer, injection or extrusion molding was observed, and better release of parts from the molds was obtained. See, also, German Published Patent Application (Offenlegungschrift) No. 2,506,667 [Chem. Abstr., 84:91066z (1976)].
Other, similar references which may be of interest include R. H. Somani and M. T. Shaw, Macromolecules, 14, 886 (1981), which describes the miscibility of polydimethylsiloxane in polystyrene; and S. N. Pandit et al., Polym. Compos., 2, 68 (1981), which reports the use of a vinyltriethoxysilane polymer as a coupling agent in glass fiber-reinforced polypropylene.
It also may be noted that polysiloxanes have been utilized in the production of nonwoven webs or fabrics, or products made therefrom, as illustrated by the references which follow.
U.S. Pat. No. 3,360,421 to S. Sands describes a bonded nonwoven backing material having perforate selvage which is used in the manufacture of carpet. In the production of the nonwoven backing material, a nonwoven web is produced from a polyolefin such as polyethylene or polypropylene. The resulting web then is subjected to bonding conditions, followed by applying to the web a lubricant which can be, among other things, methyl hydrogen polysiloxane and dimethyl polysiloxane.
A finish composition for application to a continuous filament polypropylene sheet is disclosed in U.S. Pat. No. 3,766,115 to S. Sands. The composition comprises a mixture of two polysiloxane components, the first of which is a dyeable component comprising a primary or secondary aminoalkyl- or aminoalkoxyalkylpolysiloxane fluid having an amine functionality in the range of 4-7 percent and being substantially free of other reactive groups. The second component is a lubricant component comprising a polydialkyl/arylsiloxane fluid having hydroxy end groups and being substantially free of other reactive groups. The polypropylene sheet typically is a spunbonded sheet made from isotactic polypropylene.
U.S. Pat. No. 3,867,188 to P. E. Campbell and J. G. Kokoszka relates to a spunbonded nonwoven fabric which is especially useful as a carpet backing. The fabric has on it a silicone-glycol copolymer having the general formula: EQU (CH.sub.3).sub.3 SiO{(CH.sub.3).sub.2 SiO}.sub.x {(CH.sub.3)GSiO}.sub.y Si(CH.sub.3).sub.3 in which G is a radical of the structure -R(C.sub.3 H.sub.6).sub.z OH, R is an alkylene radical containing from 1 to 18 carbon atoms, x has an average value of from 40-90, y has an average value of from 1-10, and z has an average value of from 1-10. The copolymer, a modified polysiloxane, apparently is employed as a lubricant which coats a spunbonded nonwoven fabric. The fabric, in turn, is employed as a carpet backing. The addition of the modified polysiloxane to the backing is stated to reduce damage to the backing which results from the tufting process used to manufacture the carpet.
U.S. Pat. No. 3,929,509 to H. T. Taskier describes a hydrophilic microporous film which is useful as a battery separator. The film comprises a hydrophobic microporous film coated with a silicone glycol copolymer surfactant, preferably at a level of from 2 to 20 percent by weight, based on the uncoated film. In preferred embodiments, the surfactant coating comprises a mixture of a silicone glycol copolymer surfactant and a second surfactant which preferably is an imidazoline tertiary amine. The silicone glycol copolymer surfactant preferably is a polyoxyethylene polymethylsiloxane.
A yarn finish formulation is disclosed in U.S. Pat. No. 4,105,569 to R. J. Crossfield. In preferred embodiments, the formulation contains a hydrocarbon-soluble, long molecular chain polymeric viscosity improver, such as polyisobutylene, and a polysiloxane. Preferably, the polysiloxane is an alkoxylated polysiloxane, such as a dimethylpolysiloxane with substituted polyethylene glycol or polypropylene glycol side chains or mixed polyethylene/polypropylene glycol side chains.
U.S. Pat. No. 4,563,190 to R. Topfl describes a siloxane/oxyalkylene copolymer as an optional component of a dyeing assistant for dyeing or printing polyamide fiber material with anionic dyes. See also U.S. Pat. Nos. 4,444,563 to H. Abel and 4,426,203 to H. Abel and J. Oxe.
U.S. Pat. No. 4,645,691 to I. Ona and M. Ozaki describes a method for treating materials with organopolysiloxane compounds. The method involves applying to the material a composition containing a silicone compound which has one or more alkoxysilylalkyl groups and one or more polyoxyalkylene groups. The materials to be treated preferably are fibers and fiber-containing materials.
For a limited review of similar applications of silicones, see A. J. Sabia and R. B. Metzler, Nonwovens Ind., 14, 16 (1983). Also note British Pat. No. 1,273,445 [Chem. Abstr., 77: 89559z (1972)], which describes the use of a block polysiloxane, among other materials, in the preparation of a leather substitute.
It may be noted that the above review briefly discusses polysiloxanes which have been modified by inclusion of a poly(oxyalkylene) moiety; such modified polysiloxanes can be employed in the composition of the present invention as an additive.
Additionally, polysiloxanes have been used in the manufacture of films. For example, U.S. Pat. No. 4,652,489 describes a sealable, opaque polyolefinic multi-layer film. The film is composed of a polypropylene base layer, a nonsealable surface layer, and a sealable surface layer. The nonsealable layer is a combination of a propylene homopolymer and a slip agent which preferably is a polydiorganosiloxane. The polydiorganosiloxane is used in an amount of from about 0.3 to about 2.5 percent by weight and preferably comprises a polymethylphenylsiloxane or a polydimethylsiloxane.
Finally, several references are known which are or may be of interest in relation to the additive when it contains disubstituted siloxane groups. Such references are described below.
Siloxane-oxyalkylene block copolymers are disclosed in U.S. Pat. No. 3,629,308 to D. L. Bailey and A. S. Pater. The copolymers are stated to be particularly useful as a foam stabilizer in the production of polyurethane resin foams. The copolymers are represented by the formula: ##STR1## in which R is a monovalent hydrocarbon group, R.sup.O is hydrogen or a monovalent hydrocarbon group, R' is hydrogen or a monovalent hydrocarbon group, R" is a divalent hydrocarbon group, r has a value of at least 0, m is an integer that has a value of at least 2, n is a number that has a value of at least 1 (preferably at least 4), p is a number that has a value of at least 1, there are not more than three hydrogen atoms represented by R.sup.0 in the copolymer (preferably less than one or none), and at least 25 weight-percent of the groups represented by (OC.sub.m H.sub.2m) are oxyethylene groups.
U.S. Pat. No. 4,150,013 to J. O. Punderson describes melt-processible tetrafluoroethylene copolymers containing organopolysiloxanes which are useful as wire insulation coatings. The organopolysiloxane is present in an amount of between about 0.2 and 5 percent by weight, based on the weight of the resulting copolymer composition. Representative organopolysiloxanes include polyphenylmethylsiloxane, polydimethylsiloxane, polymethylsiloxane, a copolymer of phenylmethylsiloxane and dimethylsiloxane, and the like.
A high viscosity silicone blending process is disclosed in U.S. Pat. No. 4,446,090 to E. M. Lovgren et al. The blends produced by the process are stated to have engineering properties and flame retardance superior to known blends. The process involves (a) melting a solid thermoplastic composition comprising one or more thermoplastic polymers within an extruder, (b) injecting a high viscosity silicone fluid into the molten thermoplastic composition within the extruder, and (c) blending said molten thermoplastic composition with said high viscosity silicone fluid within the extruder. The thermoplastic compositions include polyethylene and polypropylene. The silicone fluid typically is a polydimethylsiloxane. The blend can contain such additives as reinforcing fillers, antioxidants, lubricants, flame retardants, and the like. The additives can be introduced by means of the thermoplastic polymers, the silicone fluid, or both. Typical flame retardants include magnesium stearate, calcium stearate, barium stearate, antimony oxide, and decabromodiphenyloxide.
Siloxane-containing polymers are described in U.S. Pat. Nos. 4,480,009 and 4,499,149 to A. Berger. The properties of polymeric compositions are stated to be improved by the presence of a polysiloxane unit having a defined formula. The listing of polymers, however, does not include polyolefins. The disclosed compositions apparently are useful as protective coatings and as molding, extruding, laminating, and calendaring compositions. Solutions of the compositions can be used to prepare films and fibers.
U.S. Pat. No. 4,500,659 to L. A. Kroupa and E. H. Relyea relates to extrudable, curable polyorganosiloxane compositions. The compositions are similar to those of U.S. Pat. No. 4,585,830, described below. In the present case, the compositions comprise (A) a liquid triorganosiloxy end-blocked polydimethylsiloxane wherein the triorganosiloxy units are dimethylvinylsiloxy or methylphenylvinylsiloxy; (B) a reinforcing silica filler which has been reacted with a liquid or solubilized treating agent, at least one component of which is a liquid hydroxy end-blocked polyorganosiloxane wherein at least 50 percent of the silicon atoms are bonded to a fluorine-substituted hydrocarbon radical; (C) a liquid methylhydrogensiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule; and (D) a platinum-containing catalyst. The bonded treating agent for the silica filler would be incompatible, i.e., insoluble, with the polydimethylsiloxane component if it were not bonded to the silica.
Olefin polymer compositions containing silicone additives are described in U.S. Pat. No. 4,535,113 to G. N. Foster and R. B. Metzler. The compositions apparently can be extruded through relatively narrow die gaps at commercial extrusion rates to provide films having improved optical and mechanical properties. The silicone additives have the formula, EQU (R)(R)(R)Si-O-[Si(R)(R)-O].sub.x -[Si(R)(R.sup.1)-O].sub.y -Si(R)(R)(R),
in which each R, which can be the same or different, is an alkyl radical preferably having from one to six carbon atoms, R.sup.1 is a monovalent organic radical containing at least one ethyleneoxide group, vicinal epoxy group, or amino group, and x and y, which can be the same or different, each have a value of at least 1 and generally have a value of from about 4 to about 5,000. The silicone additives typically are present in the compositions in an amount of from about 0.01 to about 5 percent by weight.
U.S. Pat. No. 4,585,830 to R. P. Sweet describes polyorganosiloxane compositions useful for preparing unsupported extruded profiles. Such compositions are stated to include a triorganosiloxy end-blocked polydiorganosiloxane containing at least two vinyl radicals per molecule, in which at least 50 percent of the silicon-bonded organic radicals are methyl; and an organohydrogensiloxane containing at least two silicon-bonded hydrogen atoms per molecule, in which said hydrogen atoms are bonded to different silicon atoms. Examples of such two types of compounds are dimethylvinylsiloxy end-blocked polydimethylsiloxanes and trimethylsiloxy end-blocked dimethylsiloxane/methylhydrogensiloxane copolymers, respectively.
From the preceeding discussion, it is evident that there is a need for a single siloxane additive which will protect polymers and shaped articles made therefrom by both absorbing ultraviolet radiation and inhibiting actinic radiation-induced degradation, and which can be used as an additive in the surface-segregatable, melt-extrudable thermoplastic compositions of application Ser. No. 07/181,359.